updated certificates in tests/_samples and added script to update

removed encrypt.p12 and sign.p12 as these are not used
minor #396 fixed GH-395 - failing test discovered (sstok)

This PR was merged into the master branch.

Discussion
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fixed GH-395 - failing test discovered

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #395
| License       | MIT

Updated certificates in tests/_samples and added script to update them.

The new certs are valid for 4 years, best would be to create them for every test run but VM's have a tendency to not provide enough random entropy.

Commits
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3640c06 updated certificates in tests/_samples and added script to update